Can't upgrade IE, KB2670838 returns error 800B0100

I'll try to address your answers in order...

• Most times, I reckon such errors result from problems during the shutdown/restart phase when the system rearranges the files. If for some reason the system shuts down too soon (e.g. batteries die, or power-out) then there may be work that doesn't get done. The only thing you can do to prevent it is to make sure that you allow the machine to shut off completely before unplugging it. Other causes are memory or HD problems.
• The SURT/CheckSUR tool scans all the components of Windows - which are recorded in the registry - and checks that all references are present, and all control files present (it now also checks for 'payload' files - but makes no attempt to repair them) and attempts to correct any errors it finds. The reason that it's so large is that it contains a huge store of potential replacement files (I once tried to expand all the files, and it got to 6GB before I stopped it!)
• The trick is to have a similarly large stock of files from which to draw - my current archive weighs in at about 60GB (mostly Win7 x64 or x86, with a few Vista) from which you can cherry-pick the relevant files and then use CheckSUR to do the necessary replacement.
• Know anyone who wants to hire a 60year-old geek?
• :)

Good luck!

Post the CBS.log - I'll see what it says and maybe fix it, but I have a suspicion that I know the errors it'll show.

Yup - as expected...

Code:

 Line 5053: 2015-07-06 00:37:28, Info                  CSI    0000033c [SR] Repairing 1 components
 Line 5054: 2015-07-06 00:37:28, Info                  CSI    0000033d [SR] Beginning Verify and Repair transaction
 Line 5057: 2015-07-06 00:37:28, Info                  CSI    0000033f [SR] Cannot repair member file [l:24{12}]"utc.app.json" of Microsoft-Windows-Unified-Telemetry-Client, Version = 6.1.7601.18869, pA = PROCESSOR_ARCHITECTURE_AMD64 (9), Culture neutral, VersionScope = 1 nonSxS, PublicKeyToken = {l:8 b:31bf3856ad364e35}, Type neutral, TypeName neutral, PublicKey neutral in the store, hash mismatch
 Line 5060: 2015-07-06 00:37:28, Info                  CSI    00000341 [SR] Cannot repair member file [l:66{33}]"telemetry.ASM-WindowsDefault.json" of Microsoft-Windows-Unified-Telemetry-Client, Version = 6.1.7601.18869, pA = PROCESSOR_ARCHITECTURE_AMD64 (9), Culture neutral, VersionScope = 1 nonSxS, PublicKeyToken = {l:8 b:31bf3856ad364e35}, Type neutral, TypeName neutral, PublicKey neutral in the store, hash mismatch

MS says that these errors can be ignored, as the files concerned were accidentally tagged as static during build, rather than variable - and shouldn't even be scanned by SFC.
If you don't want to ignore them, you'll have to uninstall KB3068707 (and possibly KB3022335) and hide it/them to prevent reinstall by Windows Update.

Otherwise, the scan was clear.